Redundancy; Arrays - Adaptec DuraStor 7220SS User Manual

Redundancy

Redundancy refers to the capability of preventing data loss if a disk
drive fails. Some array types give you this capability in one of two
methods:
Two identical copies—Data is written on two disk drives,
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resulting in the same data being stored in two places. Mirror
sets, for example, use this method.
Parity—Error correcting information is distributed across
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partitions on three or more disk drives. The error correcting
information permits the system to rebuild the data if one drive
fails. RAID 5 sets, for example, use this method.

Arrays

An array, also known as a container, is two or more physical disk
drives grouped together to appear as a single device (virtual drive)
to the user. Depending on your controller, a volume set created on
a single disk drive may also referred to as an array.
An array that spans multiple physical disk drives can be larger
than any one of the physical drives. An array's underlying
partitions can be smaller than a physical disk drive. Consequently,
if the controller allows, several arrays' partitions can reside on a
single physical disk drive.
The partitions that make up an array represent used (or allocated)
space on each disk drive. The used space is available to store data,
but cannot be allocated to another array.
General Storage Concepts
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